Process of preparing lithium soaps



United States Patent PROCESS OF PREPARING LITHIUM SOAPS Application December 12, 1951, Serial No. 261,362

Claims. (Cl. 260-413) No Drawing.

This invention relates to the manufacture of soaps derived from lithium and having many uses including the compounding of such products as lubricating greases and oils.

Numerous attempts have heretofore been made to react lithium carbonate with acidogenic materials, particularly fatty materials such as fatty acids, but in all such attempts the proportion of soap produced was minute in proportion to the amount of ingredients used, resulting in less than 1% of the lithium carbonate being used in the reaction.

It is the most important object of this invention therefore, to employ lithium carbonate in a reaction whereby a lithium soap in relatively large quantities is produced.

Another important object of the present invention is to employ lithium carbonate for the production of soap in the manufacture of lubricating greases in such a manner that all, or nearly all, of the lithium carbonate is utilized.

A still further important object of this invention is to use lithium carbonate as a basic metallic salt to make a metallic soap that is economical to compound.

It has been found that lithium carbonate can be caused to react completely with acidogenic materials if there is present a small proportion of another basic material which can afterwards be volatilized. This basic material is preferably ammonia, an ammonia producing compound or an ammonia solution, although substances which react with acidogenic materials to give ammonium type compounds or decomposed through the action of heat, water or any other agent to produce substances which react with acidogenic materials to give ammonium type compounds such as carbonates of ammonia, amides of carbonia acid, urea and guanidine carbonate, primary, secondary and tertiary alkyl amines such as monoethanolamine, diethanolamine and triethanolamine respectively, primary and secondary alicyclic amines such as cyclohexylamine and dicyclohexylamine respectively, heterocyclic amines such as pyridine, primary and secondary aryl amines such as aniline and'diphenylamine respectively, acid amides such as acetamide, and acid nitriles such as acetonitrile, benzonitrile, and benzyl cyanide have been proved satisfactory.

The fatty acids found to be most effective are monocarboxylic acids such as hydroxystearic, stearic, oleic, palmitic, or various mixtures of the same, although combinations with other fatty acids both natural and synthetic may be of value. Such fatty acids may be derived from animal, marine or vegetable oils or fats or waxes or their hydrogenated products. Either pure or substan: tialiy purestearic acid or commercial stearic acid containing varying proportions of oleic, palmitic and stearic acids may be used. Also of value for production of lithium soaps are any aromatic, acidic materials such as naphthenic acids, sulfonic acids, benzoic acids, phenylacetic acids and ethyl-hexoic acids. Further illustrations include acrylic acid, crotonic acid and cyclohexyl acetic acid.

As is well known in the industry, there are two basic types of metallic soaps, the precipitated and the fused.

, 2,753,364 Patented July 3, 1956 "ice Lithium carbonate soap can result from either of the two methods. However, the precipitation method as described herein is a modification of the true precipitation method in that water is used for a purpose other than that for which it is ordinarily employed.

The procedure to be followed in bringing together the various ingredients may vary, but in the case of the modified precipitation soap method, a fundamental procedure will be outlined first with the variations following.

It has been found that .00l1.0 gram molecular weight of ammonia, calculated as NHs, is sufificient to complete the saponification of one gram molecular weight of lithium carbonate with two grams molecular weight of a fatty acid, or its equivalent of mixed fatty acids, provided some of the ammonia remains in the reaction mass until saponification is completed. In order to insure that the ammonia is retained in the mass, sufficient water to form from Lil-0.1% solution of ammonia has been found to be satisfactory. However, the amount of ammonia to be used, and as specified above, is not necessarily critical in that any amount of ammonia above the amount mentioned will react properly and the reaction will be complete.

Subsequent to saponification, the ammonia is driven off by a suitable form of heat. However, in order not to volatilize the ammonia before the reaction and saponification is complete, it is preferable to conduct the saponification within a range just above the softening point of the fatty acids. The softening point of the fatty acids, as is well known, is just slightly above their individual titer. For example, in a fatty acid, such as commercial stearic acid, the titer of softening point is 58 C. The higher the titer, the higher the softening point; the lower the titer, the less the heat requirements to obtain the sofening point.

In practicing the procedure herein specified, use of slightly less than the molar proportion of lithium carbonate is preferred when starting the reaction. After the lithium carbonate and fatty acid have completely reacted, a sufficient amount of a solution of lithium hydroxide is utilized to form a neutral soap. It is notable that lithium hydroxide is used for no other purpose than to bring the soap to the neutral point. In some cases, it has been found advantageous to finish the soap with a slight excess of acid, and in such cases, the lithium carbonate alone is used.

After saponification is complete, the mass is dehydrated, either in the presence of an oleaginous material, or without, depending of course, on whether a grease or oil is being made, or whether only a soap is to be produced which will later be compounded into other products. The oleaginous material may include any lubricating fluid such as mineral oil, which when thickened with the soap, will form lubricating oils or greases. Such lubricating fluids may include esters, both natural and synthetic, polymers and resinous materials, as well as synthetic diesters such as di-Z-ethyl hexyl sebacate, and polymers such as silicone fluids or polymerized olefins.

An important fact to note is that the lubricating fluid used to make the grease or lubricant, can be added at any time during the reaction period, i. e. at the very beginning as above specified, or preferably, later in the process. Also, the nature of the end product, wherein a grease or lubricant is desired, depends on the type and amount of lubricating fluid employed. Manifestly, therefore, any oleaginous material is suitable, enabling the compounder to tailor-make any grade grease or lubricant desired.

The formation of lithium soap by this particular process may take place in an autoclave under pressure as hereinafter set forth by specific example, but the open kettle method of saponification has the advantage that it permits the escape of carbon dioxide as the reaction proceeds to completion.

What the reaction is and through what steps it proceeds is not perfectly understood, but it is our belief that ammonia soap is first formed with the fatty acid. The lithium carbonate and the ammonia soap then enter into a double decomposition reaction which results in the formation of a lithium soap. Although it is believed that all of the ammonia soap is decomposed, traces may remain. in the finished product.

After saponification is complete, the mass is dehydrated. If the soap is to be employed as a base for a lubricating grease, this dehydration may take place in the absence of or in the presence of a portion of the mineral oil to be employed in the finished product. The higher temperatures that are applied when the mineral oil is in the mass, has two purposes. One purpose is to drive off the ammonia that remains in the grease, as well as to vaporize the water that has been used and expell it also from the mass. The second purpose is to obtain a complete dispersion of the soap in the mineral oil. When the water and ammonia have been completely driven from the mass and the soap is thoroughly dispersed, heating is discontinued and the end product is permitted to cool naturally for approximately 24 hours or the mass may be cooled in a static state or while being subjected to agitation. In both instances however, a gel stage has to be obtained before the actual end product is ready for commercial use and. application.

Some examples of the modified precipitation soap method follow:

Example 1 The following ingredients are mixed together and stirred:

50 ml. of water 2.0 grams of 28% aqua ammonia 40 grams of lithium carbonate of 98.5% purity To this mixture, 300 grams of powdered stearic acid of 58 C. titer is added and mixing continued. The stirring of the original ingredients is not critical, but is continued until a thorough mixture is obtained. The same is true after the stearic acid is added, but in the latter instance, stirring is continued until the lithium carbonate has reacted. Heat is applied to the mass until its temperature reaches 150 F. Thereafter, heat is applied from time to time as required in order to maintain the mass at 150 F. The mass is stirred continuously and maintained at this temperature for one and one-half hours when a titration shows 0.2% of free stearic acid. At this point, 150 grams of a mineral oil of 400 S. U. S. at 100 F. are added and heating resumed until the mass reaches 300 F. As previously stated, the type and viscosity of the mineral oil is not important since the particular mineral oil determines only the characteristics of the end product. Also, heating of the mass to 300 F. drives off the major portion of ammonia and water.

Further addition of mineral oil is made with continued heating until a total of 2100 grams of the oil have been added. Heat is continued until the mass reaches 400 F. This last specified temperature is obtained as stated previously, to drive ed the remainder of the ammonia and water, if any remain, and also to thoroughly mix the soap and oil. The mass is permitted to cool approximately 24 hours, the gel stage having passed before the end of such period of time. The lubricating grease of this example has an A. S. T. M. worked consistency at 77 F. of 275 and a dropping point of 361 F.

Example 2 A fire heated kettle is charged with 600 grams of stearic acid having a titer of 58 C.; to this are added 88 grams of lithium carbonate having 88.35% purity, 300: grams of water, and 2 grams of aqua ammonia having a concentration of 28% by weight. After thorough mixing, the mass is heated to 150 F. and the stirring continued for two hours. At the end of this time a titration will indicate that all the lithium carbonate has been utilized.

To this mass, 1 gram of lithium hydroxide in solution is added to bring the mass to. neutrality. Also, at this time, 30 grams of 400 S. U. S. at F. mineral oil is added. Additional heat is applied to remove the water and ammonia. When a temperature of 300 F. is attained, additional mineral oil is added at intervals and the temperature increased to 390 F. A total of 350 grams of the oil previously mentioned is used and, in addition thereto, 250 grams of an oil of 2000 S. U. S. at 100 F. is used. The use of mineral oils having two different viscosities is indicative of what has previously been said, i. e. that any mineral oil may be employed. Following the attainment of a temperature of 390 F. to 395 F., the mass is cooled. This finished lubricating grease has an A. S. T. M. worked penetration at 77 F. of 280 and a dropping point of 366 F.

Example 3 The following materials were charged into a mixer:

300. grams of stearic acid (58 C. titer) 40 grams of lithium carbonate of 98.5% purity 50 grams of water 1 gram of morpholine The above ingredients are mixed and heated to F. until saponification takes place. After titrating the mass to determine that no free fatty acid remains, 2000 grams of a mixed oil of 750 S. U. S. at 100 F. is added. The mixture is heated to 400 F. with continued stirring and subsequently allowed to cool. This finished lubricating grease has a A. S. T. M. worked penetration at 77 F. of 310 and a dropping point of 350 F.

Example 4 The following materials are charged into a mixer:

300 grams of stearic acid 58 C. titer 40 grams of lithium carbonate of 98.5% purity 50 grams of water 2.0 grams of 28% aqua ammonia 100 grams of mineral oil of 750 S. U. S. at 100 F.

These ingredients are mixed and heated to 150 F. and a titration test is made. The saponification in this example takes place as fast as that wherein the mineral oil is added after saponification, indicating that the presence of a mineral oil does not in any way inhibit the saponification reaction and also that the mineral oil may be added at any point desired. This batch is then dried by further heating, additional mineral oil having the above viscosity is added until a total of 2100 grams is obtained and the mass is heated to 395 F., after which heat and agitation are discontinued. The mass is allowed to cool and the finished lubricating grease has an A. S. T. M. worked penetration at 77 F. of 290 and a dropping point of 362 F.

cyanide.

With the compounds listed above, the following proportions and procedures may be followed:

50 grams of powdered stearic acid of 58 C. titer 7.4 grams of 89% strength lithium carbonate 0.2 gram of one of the above compounds 5.0 grams of water These ingredients are mixed, stirred and heated to 150 F. for one and one-half hours, after which 450 grams of a mineral oil of 600 S. U. S. at 100 F. is added and heating resumed until the lithium soap is dispersed in the oil. The temperature is raised to 390 F. after which the mass is cooled. Representative dropping points are 330 F. for the lubricant in which benzonitrile is used, and 365 F. in the lubricant where acetonitrile is employed. It is to be understood that any one of the above listed compounds may be used, and any amount of ammonia or ammonia-evolving compound may be employed with equally good and elfective results.

Example 6 The following ingredients are mixed together at a temperature of 70 F.:

100 grams of naphthenic acid 14.5 grams of lithium carbonate having a strength of 89% 0.1 gram of aqua ammonia 10.0 grams of water Evolution of a gas is apparent at once and the mass thickens, indicating that saponification is taking place. After the reaction subsides, heat and agitation is applied until a soap fusing at 335 F. results.

Example 7 The following example is another wherein the fusion method is adopted:

100 grams of oleic acid and 14.8 grams of 89% strength lithium carbonate are shaken in a bath held at 90 F. Into this mixture, ammonia gas is fed through a tube extended to the bottom of the container. A thickening is immediately evident and when the reaction is complete, addition of the gas is stopped and the container and mass are heated to 345 F., at which point the mass fuses, forming a lithium soap.

Example 8 The following is an example of how a lithium soap may be formed in an autoclave or similar pressure device:

grams of oleic acid 1.5 grams of 89% strength lithium carbonate 0.1 gram of aqua ammonia The above ingredients are heated to 150 F. and stirred in a sealed autoclave. The result of the stirring and heating creates a pressure which is maintained for onehalf hour. The soap produced in this manner has a melting point of 340 F.

Example 9 It has been found that an ammonium soap may be added and processed as in the examples hereinabove set forth with results as satisfactory as in the case of using either aqua ammonia or any of the other ammonia forming compounds above mentioned.

The following ingredients were first mixed at room temperature:

4 grams of naphthenic acid 0.2 gram of aqua ammonia 28% 10 ml. of water The ammonium soap was in the form of a white emulsion with no odor of free ammonia but some globules of free naphthenic acid were noted.

The following ingredients were thereupon mixed and 6 subsequently added to and mixed with the ammonium soap emulsion:

54.0 grams of commercial stearic acid of 58 C. titer 9.0 grams of 98% strength lithium carbonate 27.5 grams of 150 SUS F. oil

The mass was mixed and heated to 160 F. for two hours after which time a titration indicated 0.3% free fatty acids. At this point 0.2 gram of lithium hydroxide was added. 72.5 grams more SUS 100 F. oil was also added. The mass was heated and stirred until almost all of the water was removed. At this point 320 grams of additional 150 SUS 100 F. oil was added. The mass was then stirred and heated to 400 F. Upon cooling a consistent lubricating grease with a dropping point of 363 F. resulted.

Example 10 In lieu of aqua ammonia used in Example 1, 2.0 grams of ammonium carbonate was substituted, the remaining ingredients being the same. A lubricating grease having a 359 F. dropping point resulted.

Example 11 The steps and ingredients of Example 1 were followed and used with the exception that 2.0 grams of ammonium acid carbonate replaced the aqua ammonia of Example 1. The lubricating grease thus produced had a dropping point of 363 F.

Example 12 Two (2) grams of ammonium sesqui carbonate replaced the aqua ammonia of Example 1; a lubricating grease of 364 F. dropping point resulted.

It is to be understood that any acidogenic material may be substituted for the acids in the examples; the only change required is to determine the titer of each material so that the melting point may be determined and the proper temperature applied in the first stage of the process. Various additives, such as oxidation and corrosion inhibitors, extreme pressure compounds and the like may be added as desired within the scope of the present invention.

Having thus described the invention what is claimed as new and desired to be secured by Letters Patent is:

1. A method of producing a lithium soap which comprises the steps of admixing approximately one mole of lithium carbonate, approximately two moles of a fatty acid, and .001-1.0 mole of ammonia, calculated as NHz, from an ammonia producing compound selected from the group consisting of inorganic ammonium compounds, aliphatic, alicyclic and aromatic amines and amides, heterocyclic amines and acid nitriles, heating the mixture to obtain a reaction between said acid and the lithium carbonate, and thereupon heating the reaction mass until all of said ammonia is driven ofi.

2. A method of producing a lithium soap which comprises the steps of admixing approximately one mole of lithium carbonate, approximately two moles of a fatty acid, and a 0.1-1.0% solution of ammonium hydroxide, heating the mixture to obtain a reaction between said acid and the lithium carbonate and thereupon heating the reaction mass until all of the ammonia is driven off.

3. A method of producing a lithium soap which comprises the steps of admixing approximately one mole of lithium carbonate, approximately two moles of a fatty acid, and .001l.0 mole of ammonia, calculated as NHs, from an ammonia producing compound selected from the group consisting of inorganic ammonium compounds, aliphatic, alicyclic and aromatic amines and amides, heterocyclic amines and acid nitriles, heating the mixture to a temperature above the softening point of the fatty acid until reaction between the fatty acid and the lithium carbonate is obtained, and thereupon heating the reaction mass until all of said ammonia is driven 01f.

4. A method of producing a lithium soap which comprises the steps of admixing approximately one mole of lithium carbonate, approximately two moles of a fatty acid, and a 01-10% solution of ammonium hydroxide, heating the mixture tov a temperature above the softening point of the fatty acid until reaction between the fatty acid and the lithium carbonate is obtained, and thereupon heating the reaction mass until all. of the ammonia is driven off.

5.. A method of producing a lithium soap which cornprises the steps of admixing approximately one mole of lithium carbonate, approximately two moles of a fatty acid, and a 0-.l%-l.0% solution of ammonium hydroxide, heating the mixture at approximately 150 F. until reaction between the. fatty acid and the lithium carbonate is obtained, and thereupon heating the reaction mass at a temperature in the range of 300400 F. until all of the ammonia is driven off.

References Cited in the file of this patent UNITED STATES PATENTS Hoyt Dec. 1, Auer Aug. 14, Luckenbach Oct. 30, Morgan Dec. 4, Puryear et al. Sept. 28, Dreger et al. Mar. 1, Moore et al. Oct. 14, Kebrich et al. Sept. 1,

OTHER REFERENCES Meyer: The Role of Lithium Stearate in Greases and 

1. A METHOD OF PRODUCING A LITHIUM SOAP WHICH COMPRISES THE STEPS OF ADMIXING APPROXIMATELY ONE MOLE OF LITHIUM CARBONATE, APPROXIMATELY TWO MOLES OF A FATTY ACID, AND .001-1.0 MOLE OF AMMONIAL, CALCULATED AS NH3, FROM AN AMMONIA PRODUCING COMPOUND SELECTED FROM THE GROUP CONSISTING OF INORGANIC AMMONIUM COMPOUNDS, ALIPHATIC, ALICYCLIC AND AROMATIC AMINES AND AMIDES, HETEROCYCLIC AMINES AND ACID NITRILES, HEATING THE MIXTURE TO OBTAIN A REACTION BETWEEN SAID ACID AND THE LITHIUM CARBONATE, AND THEREUPON HEATING THE REACTION MASS UNTIL ALL OF SAID AMMONIA IS DRIVEN OFF. 